FR3042009A1 - TURBO MOTOR WITH BLOWERS DEPORTEES WITH A DIFFERENTIAL SYSTEM - Google Patents

Abstract

The present invention relates to a propulsion assembly of an aircraft comprising a turbine (15), at least one fan (10) with an axis offset from the axis of the turbine and a power transmission mechanism between the turbine and the blower, characterized in that the power transmission mechanism comprises a speed reducer (20) with an input and a movement output, the input being in line with the axis (16) of the turbine and the output connected to the blower ..

Description

Turbo fan-cooled motor with a differential system Field of the invention

The present invention relates to the aeronautical field and relates to a propulsion unit comprising at least two blowers driven by the same engine. It is more particularly a power transfer system between the engine and the blowers it drives.

State of the art

The present applicant has undertaken work on an overall propulsion architecture with two or more distributed blowers. These objectives are to seek an optimization of the propulsive efficiency thanks to a high dilution rate, while maintaining an acceptable ground clearance and small blowers at different turbine speeds.

The schematic diagram of such an assembly 1 is shown in FIGS. 1 and 2. A gas generator 3 conventionally comprises a compression assembly supplying air to an annular combustion chamber; the combustion gases from the chamber drive one or more turbines, mechanically connected to the compressor, and here a free turbine 5. The latter is secured to a power shaft 6 coaxial with the gas generator 3. This power shaft 6 drives by means of suitable bevel gears two radial intermediate shafts 8 and 8 'arranged in particular at right angles to the axis of the power shaft 6. The intermediate radial shafts each drive a fan shaft 9, 9' offset relative to the axis of the power shaft, that is to say axis offset and parallel to this axis. The transmission of power is effected by means of first gears 2 and 2 'with bevel gears between the shaft 6 and the radial shafts 8 and 8' and second gears 4 and 4 'with bevel gears between the radial shafts 8, 8 and the fan shafts 9 and 9 '. Blower shafts 9 and 9 'each drive a blower 10, 10' of axis parallel to that of the engine. Such an arrangement makes it possible to achieve the objectives referred to above.

According to the prior art known to the applicant, the solution to the transmission problem between the free turbine and the blower shafts is to use, for each of the blowers, angle gears with simple bevel gears at 45 °: A first gear , with two wheels of the same diameter, one on the shaft of the free turbine and the other on the radial shaft, and a second conical engagement at 45 ° with two wheels of different diameters connecting the radial shaft to that of the blower.

It is observed that the two blowers are inevitably run at speeds at least very slightly different even in normal situation. Indeed, in nominal operation it necessarily appears a slight asymmetry of the torques consumed in the two blowers resulting for example from a different incidence of air flows between the two blowers, different friction in the bearings, inertia and shapes slightly different vanes.

Now the kinematic diagram proposed above, is based on a simple angle transmission between the turbine shaft and two radial shafts to provide the power required blower modules. As a result, it is kinematically impossible for the two lines of fan shafts to rotate at different speeds. Such an arrangement has the consequence of causing the generation of parasitic shear stresses, potentially of very large amplitude, in the shaft lines of the blowers. The object of the invention is to develop a means capable of providing non-uniform kinematic distribution capacity between the two blowers. The invention also aims to propose a distributed multiple fan propulsion system architecture equipped with a decoupling device to dissociate the kinematic behavior of the fan shafts and thus be able to introduce differential loadings on each of them. without constraining the entire chain of transmission.

Presentation of the invention

These objectives are achieved according to the invention with a differential system comprising a housing, an axial input shaft, a planet carrier driven by the input shaft, planet gears mounted on the planet carrier, at least one gear wheel supported by the housing and radial shafts each perpendicular to the axial input shaft, the radial shafts being integral with the planet gears, the differential system being characterized by the fact that the planet carrier and the input shaft are coaxial, the planet carrier forming a hub on which the axes of rotation of the satellites are arranged radially.

The differential system of the invention has the dual advantage of reduced bulk and a balanced distribution of masses around the axis of the input shaft. These properties make the system suitable for incorporation into a turbomachine. In particular, the system proposes a volume distribution of the differential centered on the motor axis, because the available space is reduced and also centered on the motor axis. The system also has a dynamic situation close to known reducers because it does not have a large wheel rotating perpendicular to the motor axis and / or at a distance from this axis.

According to a preferred embodiment, the differential system comprises two wheels rotatable about the input shaft, each movable wheel having a first ring and a second ring gear. Advantageously but not limitatively, the first and second rings of a moving wheel being turned towards the first and second rings of the other mobile wheel, with each first ring of the movable wheels arranged vis-à-vis meshing with the gears satellites and each second ring meshing separately with one of said pinions.

In particular according to a particular embodiment, the shafts of the planet gears are arranged in planes perpendicular to the input shaft different.

According to another particular embodiment, the shafts of the planetary gears are arranged in the same plane perpendicular to the input shaft, the two second rings of the rotating wheels being then not of the same radius.

More particularly, the movable wheels each have an axial journal mounted in the housing via a bearing, in particular, the hub being supported by one of said journals via a bearing.

The applicant also aims to protect a propulsion assembly of an aircraft comprising a turbine, at least two blowers of axes offset relative to the axis of the turbine and a power transmission mechanism between the turbine and the blowers, characterized in that the power transmission mechanism comprises a differential system according to the invention between the shaft of the turbine and shafts arranged radially relative to the turbine shaft, said radial shafts each driving one of said blowers.

Preferably, the turbine is driven by the gases from a gas generator and the gas generator is a gas turbine engine with an exhaust casing comprising two concentric rings, one internal and the other external, defining between them the vein of the engine gases downstream of the turbine, the differential system being housed inside the inner shell.

In this configuration the radial shafts pass through the ferrules of the exhaust casing of the gas turbine engine.

DESCRIPTION OF THE FIGURES Other characteristics and advantages will emerge from the following description of two embodiments of the invention, which are nonlimiting, with reference to the appended drawings in which:

Figure 1 is a schematic representation of an aircraft propulsion assembly architecture;

FIG. 2 shows an arrangement of the bevel gears in the drive of the fan shaft by the turbine shaft according to the architecture of FIG. 1;

Figure 3 is a schematic representation of a differential system according to the invention;

Figures 4 and 5 show the distribution of forces on either side of the satellite wheels according to the loads applied to the drive shafts of the blowers

Figure 6 is a schematic representation of a variant of a differential system according to the invention;

Figure 7 shows an example of practical realization of the differential of the invention; and,

FIG. 8 is a perspective view in section of the differential system according to the invention

Detailed description of an embodiment of the invention

Referring to Figure 3, we see the input shaft 6 of the differential. It is connected directly to the shaft of the turbine and in the axis of the gas generator. In the extension of this axis is mounted a planet carrier 12 driven by the shaft 6. The planet carrier 12 is supported by means of appropriate bearings by the housing of the machine 17, not shown in Figure 3. This door -satellites 12 comprises around its axis and in the same plane perpendicular to it, a plurality of radial housings. In these housings are mounted the shafts 131 of satellite gears 13.

Two movable wheels 14 and 15 are mounted by bearings in the housing, their respective axis of rotation and the input shaft 6 being coaxial. The movable wheels each comprise a first ring gear, 141 respectively 151, and a second ring gear, 142 respectively 152. The first rings, 141 respectively 151, are of the same radius, arranged in two planes perpendicular to the axis of the shaft 6 being opposed to each other and spaced axially from each other so as to mesh with the planet gears 13. In other words, the first rings 141, 151 of the wheels movable 14, 15 are arranged vis-à-vis. Here, the planet gears are at 45 ° to the axis of the input shaft 6. The movable wheels 14 and 15 each carry a second ring gear, 142 and 152 respectively. The second ring gear 142 of the wheel 14 is of diameter greater than that of the first ring gear 141 and meshes with a pinion 181 of radial axis 18. The radial shaft 18 extends outwardly in the direction of a fan and drives the one of the remote blowers via a 90 ° angle gear. In the same way, the wheel 15 comprises a second ring gear 152, here of radius substantially equal to that of the ring 142 of the wheel 14. The ring 152 meshes with a pinion 191 integral with a radial shaft 19. The two shafts Radials are not placed in the same plane perpendicular to the axis of the input shaft 6. The radial shaft 19 is connected by a suitable angle gear to the drive shaft of another fan that previously axis offset relative to the axis of the input shaft 6. The pinions 181 and 191 with their respective shaft are supported by the housing 17 of the turbomachine. They form the differential gears of the differential system.

The differential system of the invention operates as follows: when the charges applied on the shafts 18 and 19 are the same, the input shaft 6 drives in rotation about its axis the planet carrier 12 and the wheels 14 and 15 by means of the planet gears 13. The second outer rotation-drive rings, separately, each a return pinion, 181 and 191 respectively and the shafts 18 and 19. In this case, the load applied externally to the shafts 18 and 18 19 is the same. As a result, the two idler gears 181 and 191 rotate at the same speed around their respective shafts, 18 and 19.

If the charges applied to the blowers are not identical, there follows an imbalance between the rotational speeds of the shafts 18 and 19 and also between the return gears 181 and 191 respectively. The moving wheels 14 and 15 are then rotated at different speeds relative to each other. This is made possible by satellites that can rotate around their axis in the carrier. The invention thus allows the driving of at least two blowers of offset axes while absorbing the differences between the loads to which they are subjected. Figures 4 and 5 illustrate the rotation of the satellites about their respective axes when an imbalance appears between the reaction forces with respect to the differential. When the charges are the same on the two blowers, FIG. 4, the forces applied on both sides on the idlers are in equilibrium and the moving wheels 14 and 15 rotate at the same speed. When the charges applied on either side of the satellites are no longer in equilibrium, the satellites 13 rotate around their axis at different speeds allowing the mobile wheels 14, 15 and the idler gears to rotate at different speeds of rotation. .

Figure 6 shows an alternative embodiment of the differential system. The two shafts 18 'and 19' each drive a fan and are arranged according to this embodiment in the same plane perpendicular to the axis of the turbine. In order to allow each of the two movable wheels 14 'and 15' to separately and individually drive one of the two shafts 18 or 19, it is then necessary for the diameters of two second rings 142 'and 152' to be different as appears on the figure. The operation is the same as in the previous embodiment.

FIG. 7 shows an exemplary practical embodiment of the differential system of the invention. It is observed that in this case the movable wheels 14 and 15 are supported by the housing 17 and each comprise a trunnion 143 and 153 respectively, each connected by ball bearings or roller bearings to the housing 17. The planet carrier 12 is supported by appropriate bearings by the journals.

In particular, in FIG. 8, where the differential system is shown in perspective and sectional view, the housing 17 is arranged to guide and hold in position the radial shafts 18, 19 and the mobile wheels 14, 15. The radial shafts 18, 19 are not in the same plane. The movable wheels 14, 15 are mechanically connected to the casing 17 by means of two bearing pairs including a ball bearing 14p1, 15p1 and a roller bearing 14p2, 15p2 which ensure their guiding in rotation. The radial shafts 18, 19 are also supported by a bearing doublet comprising a ball bearing 18p1, 19p1 and a roller bearing 18p2, 19p2. This configuration of double support (ball bearings and roller bearings) and the fact that the ball bearings are arranged closer to the teeth of the pinion gears 181, 191 and first and second rings 141, 151, 142, 152 allows to have a good quality of transmission and a good dynamic behavior. This also avoids constraints.

Claims (10)

claims A differential system comprising a housing (17), an input axial shaft (6), a planet carrier (12) driven by the input axial shaft (6), planet gears (13) mounted on the planet carrier (12), at least one gear (181, 191) supported by the housing (17) and radial shafts (18, 19) each perpendicular to the axial input shaft (6), the shafts radial (18, 19) being integral with the pinions (181, 191), characterized in that the planet carrier (12) and the input shaft (6) are coaxial, the planet carrier (12) forming a hub on which the axes of the planet gears (13) are arranged radially. 2. System according to the preceding claim comprising two wheels (14, 15) rotatable about the input shaft (6), each wheel having a first ring gear (141, 142) toothed and a second ring gear (151, 152). ), toothed, each first ring (141, 151) movable wheels (14, 15) meshing with the planet gears (13) being arranged vis-a-vis, and each second ring (142, 152) meshing separately with one (181, 191) of said idler gears. 3. System according to the preceding claim, the shafts (18, 16) of the pinion gears are placed in planes perpendicular to the input shaft (6) different. 4. System according to one of claims 1 and 2, the shafts (18,19) of the pinion gears are in the same plane perpendicular to the input shaft (6), the spokes of the two second rings (142, 152) rotating wheels (14,15) being different. 5. System according to one of claims 2 to 4, the movable rotating wheels (14, 15) each have an axial trunnion mounted in the housing through a bearing. 6. System according to the preceding claim, the hub is supported by one of said journals via a bearing. 7. A propulsion assembly for an aircraft comprising a turbine (15), at least two blowers (10) with axes offset from the turbine and a power transmission mechanism between the turbine and the blowers , characterized in that the power transmission mechanism comprises a differential gear system according to one of the preceding claims between the shaft of the turbine and shafts arranged radially relative to the shaft of the turbine, said shafts radials each driving one of said blowers. 8. propulsion assembly according to the preceding claim wherein the turbine is driven by a gas generator. 9. Propulsion assembly according to the preceding claim wherein the gas generator is a gas turbine engine with an exhaust housing comprising two concentric rings, one internal and the other external, defining the vein of the engine gases downstream of the turbine, the differential system being housed inside the inner shell. 10. Assembly according to the preceding claim wherein the radial shafts pass through the ferrules of the exhaust casing.